The imaging process utilized herein is described, with respect to a fluid jet assisted ion projection printer, in commonly assigned U.S. Pat. No. 4,463,363 issued July 31, 1984, in the names of Robert W. Gundlach and Richard L. Bergen, and entitled "Fluid Jet Assisted Ion Projection Printing". In the printer described in that patent, imaging ions are first generated and then are deposited upon a moving receptor sheet, such as paper, by means of a linear array of selectively controllable, closely spaced, minute air "nozzles". The ions of a single polarity, preferably positive, are generated in an ionization chamber by a high voltage corona discharge and are then transported, by being entrained in a high velocity fluid, to and through the "nozzles", wherein they are electrically controlled by an electric potential applied to modulating electrodes. Selective application of control voltages to the modulating electrodes in the array will establish a field across the "nozzle" to inhibit passage of ions through each "nozzle". Alternately, ions will be allowed to pass through the "nozzle", if the field is below a threshold value, so as to enable areas of charge to appear on a receptor surface for subsequent development.
A typical modulating structure for this type of printer is disclosed in commonly assigned U.S. Pat. No. 4,524,371 issued June 18, 1985 in the names of Nicholas K. Sheridon and Michael A. Berkovitz and entitled "Modulation Structure for Fluid Jet Assisted Ion Projection Printing Apparatus". The modulating structure is formed upon a planar marking head, illustrated in FIGS. 7, 8 and 9, mounted on the ion-generating housing, and each electrode thereon may be addressed individually for modulating each "nozzle" independently.
An improved, integrated, printer marking head, incorporating thin film ion-modulating electrodes, drive circuitry, and switching elements formed upon a single substrate is disclosed in copending commonly assigned U.S. patent application Ser. No. 639,983, filed Aug. 13, 1984 in the names of Hsing C. Tuan and Malcolm J. Thompson, entitled "Marking Head for Fluid Jet Assisted Ion Projection Imaging Systems", now U.S. Pat. No. 4,584,592.
The printers described in the Gundlach et al and the Sheridon et al patents and the Tuan et al application rely upon the selective imposition of electrical data on their modulation electrodes. The data may be computer generated and/or controlled and is normally applied by any conventional data-addressing technique.
In yet another copending, commonly assigned, U.S. patent application Ser. No. 646,549 filed Sept. 4, 1984 in the names of Gene F. Day and Lloyd D. Clark, entitled "Ion Projection Copier", now, U.S. Pat. No. 4,591,885 the principle of the fluid jet assisted ion projection marking process is incorporated in an apparatus for copying original images onto an image receptor. This is accomplished by causing an optical input to address a photoconductive modulation assembly formed at one end of a lightcollecting ribbon.
U.S. Pat. Nos. 3,323,131 (MacGriff) and 3,594,162 (Simm et al) are also of interest, as they relate to the use of photoconductive materials for controlling electrographic charge deposition. In the MacGriff patent, an image-control device comprises a light-sensitive layer sandwiched between a transparent electrode layer and individual conductive stripes. Optical images are projected upon the control device for controlling the emission of the conductive stripes. In Simm et al, the lip of a projection gap has a photoconductive strip formed thereon for controlling the field across the gap, to affect the passage of ions through the gap.
It would be desirable to provide an inexpensive, highly reliable electronic copier in which the construction of the modulation electrodes and their relationship to the optical sensing structure is greating simplified relative to the Day et al structure. To that end, it is the primary object of the present invention to provide a marking head, for controlling the flow of ions through the ion projector, having integrally fabricated thereon thin film elements, including modulating electrodes, a photosensor circuit associated with each electrode, and suitable bus lines.